One shot multivibrator



R. B. TROUSDALE 2,778,936

ONE SHOT MULTIVIBRATOR Jan. 22, 1957 Filed Aug. 27, 1952 Bal/'ce Signa INVENTOR.

14h10/wey 2,718,936 ONE snor MULTIvrRAToR Robert B. Trousdale, Webster, N. Y., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application August 27, 1952, Serial No. 306,691

8 Claims. (Cl. Z50-27) The present invention relates to multivibrators and more particularly to a one-shot multivibrator employing gas tubes or tubes of the type including an ionizable medium. This application is a continuation-inpart of my co-pending application Serial No. 140,927, led on Iannary 27, 1950 and assigned to the same assignee as the present invention.

Multivibrators have come into extensive use in recent years as a source of square waves, as an electronic switch, and for other purposes. Many times it is desirable to cause an electronic switching operation or the like in response to the receipt of a single pulse after which it is desired for the circuit to be restored to its original quiescent condition until another pulse is received. It would be desirable to provide an arrangement in which an extremely high power output can be obtained in response to the receipt of each trigger pulse and in which the electronc circuit may readly be adapted for inverter operation or the like. Such an arrangement is particularly useful as a high power signal source for the ringing facilities, harmonic or otherwise, of an automatic telephone system.

Accordingly, it is an object of the present invention to provide a new and improved one-shot multivibrator.

It is another object of the present invention to provide an improved arrangement for initiating a cyclic operation upon receipt of a single trigger pulse in connection with a pair of vapor electric discharge valves.

It is a further object of the present invention to provide a one-shot multivibrator employing gas tubes in which an extremely high power output can be obtained.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specifica* tion.

For a better understanding of the present invention reference may be had to the accompanying drawing in which 'the single iigure is a schematic diagram of one embodiment of the present invention.

The present invention contemplates the employment of a pair of gas or so-called vapor electric discharge valves of the thyratron type connected into a circuit which is triggered in response to the receipt of a single pulse and which immediately shuts itself ott, depending upon the time constant of the circuit, so as to reach and remain in a quiescent condition until another pulse is received.

Referring now to the drawing, there is illustrated an electronic discharge valve 1i) which serves to control the supply energy from a source of B-lpotential 11 to a utilization circuit generally designated at 12. Effectively, electronic discharge valve lil acts as an electronic switch so that when rendered conductive, it supplies the full potential of the high power B+ source 11 to the utilization circuit 12, except for the small voltage drop through the valve which is probably ot the order of 10 volts or the like. Electronic discharge valve 10 is illustrated as ICC of the type containing an ionizable medium such as a gas or a vapor which is characterized by the tact that once rendered conductive by the control electrode, the valve remains conductive until the anode-to-cathode voltage is reversed or the anode circuit is interrupted. As illustrated, electronic discharge valve 10 comprises an anode 13, a cathode 14, a control electrode or grid 15 and a shield grid 16. The cathode 14 has its cathode terminal 17 connected to ground indicated at 18 through a suitable load resistor 19. When electron discharge valve 10 is rendered conductive, substantially the full potential of the source 11 except for the small potential drop through the valve 10 appears across the load resistor i9 and is supplied to the utilization circuit 12 as indicated. The shield grid 16 is connected to the cathode 14 in the conventional manner.

For the purpose of controlling the discharge through electron discharge valve 10, the control electrode 15 isl connected to a source of input signal generally designated at 2t? through a suitable coupling capacitor 21. A negative biasing potential from the source generally designated at 22 is supplied to the control electrode Y15 through a urrent limiting resistor 23. The magnitude of the negative potential of the source 22 is controlled so as to maintain electron discharge valve 10 non-conductive under normal conditions. Upon the receipt of a signal pulse in the form of a positive pulse as indicated in the single figure of the drawing, the potential of the' control electrode 15 is momentarily raised to a suiiciently great extent as to render electron discharge valve 1t) conductive whereupon the negative biasing potential from the source 22 is incapablev of `terminating the conductive operation ot the valve 10 even though no further signal pulse is received. With the arrangement described thus far, theretore, electron discharge valve 1t) effectively comprises an electronic switch for supplying potential to the utilization circuit 12 in response to the receipt of a single positive pulse from the input signal source 2t). Without more, however, the electron discharge valve 10 will remain conductive once it is rendered conductive unless the source of anode potential is effective removed.

yFor the purpose of terminating the conducting characteristic of electron discharge valve 1) once it has been rendered conductive, there is provided a second electron discharge valve 25 also of the vapor discharge type and preferably identical with the electron discharge valve 10. As illustrated, electron discharge valve 25 comprises an anode 26, a cathode 2'7, a control electrode or grid 28 and a shield grid 29. To prevent electron discharge valve 25 from being conductive except substantially during the time that electron discharge valve lil is conductive the anode 26 is connected to the cathode terminal 17, which is also the ungrounded terminal of the load resistor 19, through a suitable current limiting resistor 30. Effectively, therefore, the anode 26 is connected to the cathode 14 so that electron discharge valves 19 and 25 are arranged with their plate circuits in series circuit arrangement. The cathode 27 is connected to ground 31 through a suitable .cathode resistor 32.

A suitable capacitor 33 for use as a temporary source of high plate. currents through the tube 25 is connected .between the plate 26 and ground. The shield grid 29 of the electron discharge valve 25 is connected to a suitable source of potential designated as negative potential source 34 through a current limiting resistor 35. The control electrode 23 of electron discharge valve 25 is connected to the load resistor terminal 17 through a suitable timing resistor 37 and to ground designated at 38 through a suitable timing condenser 39. With this arrangement it will be apparent that when electron discharge valve 10 is rendered conductive a charging circuit for capacitor 39 through resistor 37 is provided and the capacitance and the resistance of the resistor 37.

3 charging time for condenser 39 is dependent upon T1ilts e one-shot multivibrator circuit is completed by the addition of a capacitor 40 interconnecting the cathode 2.7 of electron discharge valve 25 with the load resistor terminal 17. This capacitor 40, as will become apparent from the following description, effectively is an arc eX- tinguishing capacitor for extinguishing the discharge through electron discharge valve 10.

When no signal is supplied from the input 20 through the coupling capacitor 21, electron discharge valves and 25 are non-conducting by virtue of the negative bias applied to the control electrode from source 22 and the further fact that electron discharge valve 25 cannot be rendered conductive without electron discharge valve 10 having rst been rendered conductive. Under these conditions the capacitor 33 is discharged through resistors 30 and 19, the capacitor 39 is discharged through the resistors 37 and 19, fand `the capacitor 40 is discharged through the resistors 32 and 19. Moreover, under these conditions the potential at terminal 17 of load resistor 19 is zero and consequently no potential is supplied to the utilization circuit 12. Upon the receipt of a signal such, for example, as a positive pulse from the input 20, the control electrode 15 is momentarily rendered suiciently positive to cause electron discharge valve 10 -to re, whereby current ows through the load resistor 19 and substantially the entire potential of the source 11 is supplied to the utilization circuit 12. This potential is also supplied to the plate circuit of electron discharge valve 25 through the resistor 30, but by virtue of the negative biasing potential on the shield grid 29 electron discharge valve 25 remains nonconductive. The drop across load resistor 19 applies a potential across the timing circuit comprising resistor 37 and capacitor 39 which in `turn causes capacitor 39 to charge to a suiciently high potential which is applied to the control electrode 28 to render electron discharge valve 25 conductive, whereupon current flows through resistors 30 and 32 in the plate circuit of valve 25.

Capacitor 33 is charged through the resistor 30 to the potential of terminal 17 as soon as the valve 10 is tired. Accordingly, when the valve 25 is red in the manner described above, the capacitor 33 acts as a temporary source of plate potential for the valve 25 and current flows over a path which includes the capacitor 33, the space current path of the valve 25, the capacitor 40 and the resistor 19 to the grounded terminal of the capacitor 33. This additional current flow through the resistor 19 raises the potential of the terminal 17 by an amount suflicient to extinguish the valve 10 by reversing the anode-cathode potential impressed thereon. In this connection it will be understood that when the valve 25 tires the potential drop through the valve 25 is relatively small and `the potential across the capacitor 33 cannot be changed instantaneously so that substantially the full anode potential on the valve 25 is impressed upon the resistor 19 the instant the valve 25 res. Electron discharge valve 25 will continue to conduct current until capacitor 33, which has been charged, discharges, which is only for a very short time and immediately capacitors 39 and 40 will discharge through resistors 37, 19 and 32, 19 respectively. The entire circuit is thereby restored to its initial condition and will remain so until a new trigger pulse is received.

Preferably electron discharge valves 10 and 25 are hot cathode type valves whereby it is possible to obtain an extremely high power output. Furthermore, the circuit may readily be adapted for inverter operation, particularly if arranged in a push-pull configuration.

While it will be apparent that the impedance values of the several circuit elements of the above-described system may be varied within wide limits in accord-ance with the particular requirements and desired characteristics .of the system, the following constants for the control circuit of the present invention have been found to be satisfactory for a particular installation:

Condenser 21 .0001 microfarad. Condenser 33 .01 microfarad. Condenser 39 .1 microfarad.

Condenser 40 .0l microfarad. Electron discharge valve 10 5696 (R. C. A.) type. Electron discharge valve 25 5696 (R. C. A.) type. Resistor 19 100,000 ohms. Resistor 2.3 1 megohm.

Resistor 30 1 megohm.

Resistor 32 10,000 ohms. Resistor 35 l megohm.

1Resistor 37 2.2 megohms.

The value of the resistance of resistor 37 and the capacitance of capacitor 39 may be Varied in order to vary the length of time which elapses between ring of electron dischargetube 10 and tiring of electron dis-I In the event that the multivibrator v charge valve 25. described is used as a source of square waves, the time delay provided by the timing circuit will control the width of each half cycle of the square wave. It will be understood that the present invention also lends itself to use as an electronic switch for producing a gating voltage.

While there has been illustrated and described a particular embodiment of the present invention, it will be understood that various changes and modifications will occur to those skilled in the art. pended claims to cover all such changes and modifications =as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. ln combination, a potential supply circuit, a utilization circuit, an electronic switch comprising a first electron discharge valve `of the gas type for connecting said supply circuit to said utilization circuit, said valve having a control electrode, a signal source connected to said control electrode, the receipt of a predetermined signal from said signal source rendering said electronic switch elective to interconnect said supply and utilization circuits, a second electron discharge valve of the gas type, means for connecting the plate of said second valve to the cathode of said iirst valve, means including a capacitor for ring said second valve, and means including said connecting means for extinguishing .the discharge through said rst valve in response to the discharge through said second valve, the iiow of current through said second valve being immediately terminated following extinguishment of the discharge through said first valve due to automatic removal `of plate potential therefrom.

2. A gas tube one-shot multivibrator comprising ay potential `supply circuit, a utilization circuit, an electronic switch comprising a first electron `discharge valve of the gas type for connecting `said supply circuit to said utilization circuit, said valve having a control electrode, a signal source connected to said control electrode, the receipt of a predetermined signal from said signa-l source rendering said electronic switch effective to interconnect said supply and utilization circuits, a second electron discharge valve of the gas type, means for connecting the plate of said second valve to the cathode of said first valve, a cathode resistor in circuit with .said second valve, a capacitor connected rbetween the cathode of said rst valve and the cathode of said second Valve so as to be charged through said cathode resistor upon firing of said iirst valve, and means for momentarily producing a relatively high potential across said cathode resistor upon tiring of said second valve whereby the vsum of the potentials across said capacitor and cathode resistor causes extinguishment of the discharge through said rst valve.

3. in combination, a source of potential, a load impedance, an electron discharge valve having an anode, al

It is aimed in the apcathode and a control electrode interconnecting said source and said load impedance, a signal source connected to said control electr-ode for `rendering said electron discharge valve conductive, a second electron discharge valve having its plate circuit connected in parallel with said load impedance, an anode resistor and a cathode resistor included in said plate circuit, each of said electron discharge valves being of the type containing an ionizable medium, a capacitor, a charging circuit for said capacitor including said cathode resistor, means for connecting said charging circuit in parallel with said load impedance, and a capacitor eliectively shunting said anode resistor to provide a momentary low impedance path through said second electron discharge valve following ring `of said first valve whereby the potential across said charging circuit is momentarily raised sufficiently to extinguish the discharge through said iirst va'lve.

4. A one-shot multivibrator comprising a potential supply circuit, a utilization circuit, an electronic switch comprising a first electron discharge valve for connecting said supply circuit to said utilization circuit, said Valve having a control electrode, a signal source connected to said control electrode, the receipt of a predetermined signal from said signal source rendering said electronic switch effective to interconnect said supply and utilization circuits, a second electron discharge valve, means for connecting the plate of said second valve to the cathode of said iirst valve, a cathode resistor in circuit with said second valve, a capacitor connected between the cathode of lsaid first valve and the cathode of said second valve so as to be charged through said cathode resistor upon firing of said iirst valve, and means comprising a capacitive impedance in the plate circuit of said second valve for causing extinguishment of the discharge .through said first valve upon tiring of said second valve.

5. A gas tube one-shot multivibrator comprising a potential supply circuit, a utilization circuit, an electronic switch comprising a tirst electron discharge valve of the gas type for connecting said supply circuit to said utilization circuit, said valve having a control electrode, a signal source connected to said control electrode, the receipt Iof a predetermined signal from said signal source rendering said electronic switch effective to interconnect -said supply and utilization circuits, a second electron discharge valve of the gas type, means for connecting the plate of said second valve to the cathode of said first valve, a cathode resistor in circuit with said second valve, a capacitor connected between `the cathode of said rst valve and the cathode of said second valve so as to be charged through said cathode resistor upon tiring of said rst Valve, time delay means for ring said second valve a predetermined time after tiring of said tirst valve, and means for momentarily producing a relatively high potential across said cathode resistor upon tiring of said second valve whereby the sum of the potentials a-cross said capacitor and cathode resistor causes extinguishment of the discharge through said irst Valve.

6. In combination, a source of potential, a load impedance, an electron discharge valve having an anode, a cathode and a control electrode interconnecting said source and said loa-d impedance, a signal source connected to said control electrode for rendering said electron discharge valve conductive, a second electron discharge valve having its plate circuit connected in parallel with said load impedance, a cathode resistor for said second discharge valve included in said plate circuit, each of said electron discharge valves being of the type containing an ionizable medium, a capacitor, a charging circuit for said capacitor including said cathode resistor, means for connecting said charging circuit in parallel with said load impedance, and means responsive to firing of said second valve for causing the potential across said charging circuit to be raised sufliciently to extinguish the discharge through said irst valve.

7. In combination, a source of potential, a load impedance, an electron discharge valve having an anode, a cathode and a control electrode interconnecting said source and said load impedance, a signal source connected to said control electrode for rendering said electron discharge valve conductive, a second electron discharge valve having its plate circuit connected in parallel with said load impedance, a cathode resistor for said second discharge valve included in Isaid plate circuit, a capacitor, a charging circuit for said capacitor including said cathode resistor, means for connecting said charging circuit in parallel with said load impedance, -time delay means including a capacitor paralleling said -load impedance for controlling the tiring of said second valve a predetermined time after firing of said first valve, and means responsive to the potential across said charging circuit following discharge through said second valve for extinguishing the discharge .through said iirst valve.

8. In combination, a source of potential, a load impedance, a iirst electron discharge valve having an anode, a cathode and a control electrode interconnecting said source 'and said load impedance, a signal source connected to said control electro-de for rendering said tirst electron discharge valve conductive, a second electron discharge valve having its plate circuit -connected in parallel with said load impedance, a cathode resistor for said second discharge valve included in said plate circuit, each of said electron discharge valves being of the type containing an ionizable medium, a capacitor connected between the cathode .of said first valve and `the cathode of said Isecond Valve so as to be charged through said cathode resistor upon tiring `of said Iirst valve, and time delay means for tiring said second valve a predetermined time after firing of said first valve so that the flow of current through said second .tube produces a relatively high potential across said cathode resistor, the sum of the potentials across said cathode resistor and said capacitor being suicient `to cause extinguishment of the discharge through said rst Valve.

References Cited in the tile of this patent UNITED STATES PATENTS 2,419,340 Easton Apr. 22, 1947 2,496,543 Kanner Feb. 7, 1950 2,596,142 Gerwin May 13, 1952 2,629,823 Grandmont Feb. 24, 1953 2,686,262 Wiley Aug. 10, 1954 FOREIGN PATENTS 487,982 Great Britain June 29, 1938 

